Biodegradation of Partially Hydrolyzed Polyacrylamide HPAM Using Bacteria Isolated from Omani Oil Fields

Abstract

Abstract In present study the biodegradation of partially hydrolyzed polyacrylamide (HPAM) by bacterial strains isolated from Omani oil fields was analyzed. HPAMs are extensively used in oil fields for enhanced oil recovery operations. The produced water after polymer flooding poses grave ecological problems, such as it could raise the difficulty of oil–water separation, producing toxic acrylamide that degrades naturally, which threatens the local environment. Biodegradation of HPAM by microbes may be an efficient way to solve those problems. Microbial biodegradation is considered an environmentally friendly safe technique. The isolation of microbes that are able to degrade HPAM from the oil field produced water was investigated in this study. The bacterial isolates were identified by MALDI-Biotyper and the biodegradation of HPAM was analyzed by LC-MS and reduction in viscosity by rheometer. Two HPAM degrading bacterial strains Bacillus sp. (NP-10) and Chelatococcus sp. (NP-11) were isolated from the polymer-flooding produced water. The removal efficiency of HPAM based on shear viscosity for NP10 andNP11 were 59.9% and 58.4%, respectively after 9-days treatment period, at pH 7.1, 40 °C and 160 rpm. The addition of glucose (0.5 g/l) did not improve the HPAM degradation for NP11. However, the degradation percentage by NP10 reached to 68.8%. HPAM samples after bacterial biodegradation were analyzed by LC-MS. The results showed the presence of acrylamide monomers in the culture after biodegradation. Three other isolated strains were identified as NP-9, NP-2 and NP-8 were able to reduce the concentration of acrylamide significantly. Present findings proved that both Bacillus sp. (NP-10) and Chelatococcus sp. (NP-11) could be suitable candidates for biodegradation of HPAM and NP-9, NP-2 and NP-8 strains as potential candidates for reducing the acrylamide concentrations, as an environmental friendly approach.